In recent years, materials for electrical and electronic equipment parts, materials for automobile equipment parts, materials for chemical equipment parts, and the like have been requested to be thermoplastic resins having high heat resistance. Although liquid crystalline polyester resins belong to the resins which meet the requirement, these resins are used in a large quantity for precision-molded articles because of good flowability and small shrinkage during solidifying from the molten state thereof. However, due to the fact that there are a large number of complex-shape molds for the molded articles, there arises a problem of deteriorated productivity, because of poor releasability of these liquid crystalline polyester resins from molds during the molding operation, difficulty in the stable continuous molding operations of the resins, and slow molding speed (molding cycle). With the above situation, mold-releasability of the liquid crystalline polyester resins is still insufficient, though it is better than that of other resins.
As a common practice for improving the mold-releasability, there is a method to add a mold-release improving agent to resin. There are known mold-release improving agents such as:
(1) a method for adding a metal salt of a fatty acid such as zinc stearate or lithium stearate; (2) a method for adding an ester of fatty acid such as glycerol tristearate; and (3) a method for adding an amide of fatty acid such as N,N′-alkylenebisalkane amide. However, even though the releasing effect is observed in any of these (1), (2) and (3) methods, the thermal decomposition temperature of the mold-releasing agent is lower than the molding-processing temperature of the liquid crystalline polyester resin. There are problems such as a discolored molded article, deteriorated mechanical properties and gas generation at the time of kneading-processing and molding, caused by the decomposition of the mold-releasing agent.
To solve such problems, Japanese Patent No. 2915915 proposed adding a specific higher fatty acid ester.